ARTICLE
Auteur(s) : Yasuhiro KAWACHI kyasuhir@md.tsukuba.ac.jp,
Ryota TANAKA, Yasuhiro FUJISAWA, Junichi FURUTA, Yasuhiro NAKAMURA,
Yoshiyuki ISHII, Fujio OTSUKA
Department of Dermatology, Institute of Clinical Medicine,
University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8575,
Japan
Malignant peripheral nerve sheath tumor (MPNST) is a rare type
of sarcoma that usually arises de novo in the deep soft
tissues or in association with deep-seated diffuse/nodular
plexiform neurofibromas in neurofibromatosis type I (NF1) [1].
These lesions rarely arise in association with superficial
cutaneous neurofibromas. Here, we report a case of superficial
MPNST arising from a solitary cutaneous neurofibroma in a non-NF1
patient.
A 62-year-old woman, with no history of NF1, was referred to our
clinic due to cutaneous tumors on the left upper back. A
pedunculated soft tumor was first noticed 23 years previously. The
size and appearance of the tumor had not changed for at least 10
years. However, she recently noticed another subcutaneous hard mass
beneath the preexisting tumor two months prior to referral, which
enlarged rapidly over a period of two months. Clinical examination
revealed a dark-erythematous pedunculated soft tumor 2 cm in
diameter on her left upper back (figure 1A).
A slightly elevated skin-colored subcutaneous hard induration was
observed beneath the pedunculated tumor (figure 1A,
dotted line). Excisional biopsy, including the two tumors, was
performed. Microscopically, the lesion was composed of two
components: a dermal fibrous tumor protruding from the skin and a
subcutaneous tumor with a central basophilic hypercellular area
(figure
1B). There was an abrupt transition from the less
cellular fibrous component in the upper dermis to the more cellular
component in the deep dermis and subcutaneous tissue (figure 1C,
dotted line). The preexisting pedunculated tumor was shown to
be a conventional neurofibroma within the upper to deep dermis,
consisting of spindle-shaped cells with pale eosinophilic cytoplasm
and wavy nuclei (figure 1D).
The hypercellular areas of the subcutaneous tumor consisted of
round and polygonal epithelioid cells, with hyperchromatic and
polymorphous nuclei. There were numerous mitotic figures (figure
1E). Immunohistochemical staining revealed that the
hyperchromatic cells of the subcutaneous tumor were diffusely
positive for neuron-specific enolase (NSE) (figure 1F).
They were also focally positive for S-100 protein, but negative for
desmin, α-smooth muscle actin (α-SMA) or CD34 (data not shown).
Fifteen percent of the hyperchromatic cells in the subcutaneous
tumor were positive for Ki-67 (figure 1G),
while most of the neurofibroma cells were Ki-67-negative (figure
1H). The neurofibroma cells were positive for S-100
protein (figure 1I).
Based on these findings, we made a diagnosis of superficial MPNST
arising in a solitary neurofibroma. Additional surgical excision
with 3-cm margins from the remaining tumor edge was performed.
Neither local recurrence nor distant metastasis has been observed
during 3 years of follow-up.
MPNST is a rare type of sarcoma that accounts for 5%-10% of all
soft tissue sarcomas, and has an incidence rate of 0.001% in the
general population. This tumor type is strongly associated with
NF1, with about 25%-50% of MPNST cases occurring in association
with NF1 [1, 2]. MPNSTs are generally regarded as sarcomas
that occur in the deep soft tissue. Most MPNSTs arise in
association with deeply situated major nerve trunks, including the
sciatic nerve, brachial plexus, and sacral plexus. In NF1, MPNSTs
may arise in preexisting plexiform neurofibroma, most of which are
deeply seated. Superficial MPNSTs arising from cutaneous peripheral
nerves or cutaneous neurofibroma are extremely rare, and only a
limited number of MPNSTs developing from cutaneous neurofibroma
have been reported in the literature [3-5]. To our knowledge, this
is the first report of superficial MPNST arising in association
with a solitary neurofibroma in non-NF1. Although progression of
plexiform neurofibroma in NF1 into MPNST is well established, the
histopathological direct transition of neurofibroma to MPNST in the
present case indicates the strong linkage between neurofibroma and
MPNST.
Most MPNSTs show poor prognosis with a high rate of local
recurrence and distant metastasis. However, as in our case, the
behavior of superficial MPNST is generally good, probably because
of its superficial location, and these tumors can be clinically
noticed at an early stage.
Disclosure
Financial support: none. Conflict of interest: none.
References
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3 KH Allison, RM Patel, JR Goldblum, B.P. Rubin Superficial
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4 K Li, CH Won, S.E. Moon A superficial form of malignant
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5 C Thomas, N Somani, LG Owen, JC Malone, S.D. Billings
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